Luca Piciullo

Definition and performance of a threshold-based regional early warning model for rainfall-induced landslides

A process chain for the definition and the performance assessment of an operational regional warning model for rainfall-induced landslides, based on rainfall thresholds, is proposed and tested in a landslide-prone area in the Campania region, southern Italy. A database of 96 shallow landslides triggered by rainfall in the period 2003–2010 and rainfall data gathered from 58 rain gauges are used. First, a set of rainfall threshold equations are defined applying a well-known frequentist method to all the reconstructed rainfall conditions responsible for the documented landslides in the area of analysis. Several thresholds at different exceedance probabilities (percentiles) are evaluated, and nine different percentile combinations are selected for the activation of three warning levels. Subsequently, for each combination, the issuing of warning levels is computed by comparing, over time, the measured rainfall with the pre-defined warning level thresholds. Finally, the optimal percentile combination to be employed in the regional early warning system, i.e. the one providing the best model performance in terms of success and error indicators, is selected employing the “event, duration matrix, performance” (EDuMaP) method.

The Community-Based Alert and Alarm System for Rainfall Induced Landslides in Rio de Janeiro, Brazil

The community-based alert and alarm system for rainfall induced landslides in Rio de Janeiro, locally called A2C2 (Sistema de Alerta e Alarme Comunitario para Chuvas Fortes), may be considered the second tier of the citywide landslide early warning strategy initiated, between the late 1980s and the early 1990s, with the SIGRA and the—still operational—Alerta-Rio projects. The A2C2 landslide early warning system was deployed between 2011 and the first few months of 2012; it is currently employed in 103 informal communities of the city. Herein, the main characteristics of the A2C2 system are presented together with a preliminary analysis on its behaviour during this initial phase of deployment.

Regional Landslide Early Warning Systems: Comparison of Warning Strategies by Means of a Case Study

Two categories of landslide early warning systems can be defined as a function of the scale of analysis: local systems and regional systems. Landslide warning systems operating at regional scale are almost exclusively implemented for rainfall-induced landslides and they typically assess the probability of occurrence of landslides over appropriately-defined homogeneous alert zones using both atmospheric monitoring data and rainfall predictions. The paper focuses on such systems, by presenting a comparison of the performance of two regional landslide warning models (ReLWaM) designed considering different algorithms. The evaluation of the performance of the different models is conducted applying the EDuMaP method, which is based on the computation of a duration matrix reporting the time associated with the occurrence of landslide events in relation to warning events, in their respective classes. Two different ReLWaMs have been employed for a case study in the Campania Region (Italy), considering the six-year time frame 2010–2015. The rainfall measurements and the data on landslides were derived respectively from the TRMM project database, which reports 3-hourly rainfall data, and from the project “Franeitalia”, an inventory of Italian landslides with information retrieved from on-line journalistic sources.

Monitoring strategies for local landslide early warning systems

The main aim of this study is the description and the analysis of the monitoring strategies implemented within local landslide early warning systems (Lo-LEWS) operational all around the world. Relevant information on 29 Lo-LEWS have been retrieved from peer-reviewed articles published in scientific journals and proceedings of technical conferences, books, reports, and institutional web pages. The first part of the paper describes the characteristics of these early warning systems considering their different components. The main characteristics of each system are summarized using tables with the aim of providing easily accessible information for technicians, experts, and stakeholders involved in the design and operation of Lo-LEWSs. The second part of the paper describes the monitoring networks adopted within the considered systems. Monitoring strategies are classified in terms of monitored activities and methods detailing the parameters and instruments adopted. The latter are classified as a function of the type of landslide being monitored. The discussion focuses on issues relevant for early warning, including appropriateness of the measurements, redundancy of monitoring methods, data analysis, and performance. Moreover, a description of the most used monitoring parameters and instruments for issuing warnings is presented.